1. Field of the Invention
The invention relates to valves in general, hydraulic valves in particular, and especially to a control valve for a hydraulic torque wrench with a hydraulic spin down motor.
2. Prior Art
The use of hydraulic wrenches to tighten (make up) or loosen (break out) nuts or bolts in high torque applications, such as the erection of off shore risers is well known. See, e.g., U.S. Pat. No. 4,448,096, which is hereby incorporated by reference. These wrenches are well suited to the task of supplying the high torques needed in these applications, however, they are very slow in turning the bolt or nut being tightened or loosened. This is not a problem when the nut or bolt is snug, as very little additional rotation (≲1 full rotation) is all that is usually required to either reach the desired torque or to loosen the nut/bolt to the point that the high torque wrench is no longer needed to turn the nut/bolt. However, when the nut or bolt is not snug, the hydraulic torque wrench can be painfully slow. In the prior art, hydraulic torque wrenches were frequently removed after the bolt/nut was loosened and a low torque spin down wrench would then be used to back the bolt/nut out. Similarly, the low torque spin down wrench might be used to spin the bolt/nut down until it was snug, and then the hydraulic torque wrench would be used to fully tighten the bolt/nut. These wrenches are typically quite large, and changing them out constantly during a job can be expensive and time consuming. In response to these inconveniences, hydraulic torque wrenches that included a self-contained spin down motor were developed. See, e.g., U.S. patent application Ser. No. 09/302,836, which is hereby incorporated by reference in its entirety. However, the prior art combined wrenches, such as that disclosed in PCT/US94/14715, had numerous problems. Some of the problems included complicated and expensive hydraulic controls, troublesome back pressure valves, and an inability to use hydraulic sources already in place, such as the drilling rig hydraulic lines. Accordingly, a hydraulic control system that meets the following objects is desired.
It is an object of the invention to provide a control system for a combination hydraulic torque wrench and spin down motor.
It is an object of the invention to provide a control system for a combination hydraulic torque wrench and spin down motor which will only run the spin down motor when the hydraulic torque wrench is retracted.
It is an object of the invention to provide a control system for a combination hydraulic torque wrench and spin down motor that will only extend the hydraulic torque wrench when the spin down motor is off.
It is an object of the invention to provide a control system for a combination hydraulic torque wrench and spin down motor that does not require a back pressure valve.
It is an object of the invention to provide a control system for a combination hydraulic wrench and spin down motor that will operate on rig hydraulics.
It is an object of the invention to provide a control system for a combination hydraulic torque wrench and spin down motor that does not require a control console separate from the wrench.
The invention is intended for use with a hydraulic torque wrench having a built in run down motor. The hydraulic torque wrench essentially comprises a drive head having a socket configured to engage a threaded member such as a bolt or a nut. The drive head has a plurality of ratchet teeth radially positioned on the drive head. A hydraulic cylinder is configured to extend and retract a drive pawl which engages the ratchet teeth upon extension and thus rotates the drive head. Rotation of the drive head results in the rotation of the socket and the threaded member which the socket has engaged. Very high pressures can be exerted against the drive head with the hydraulic cylinder, resulting in torques in the range of about 10,000 to upward of 34,000 ft. lbs. being applied to the threaded member being tightened or loosened. Examples of this type of torque wrench can be found in U.S. Pat. No. 4,448,096.
The spin down motor is also preferably hydraulically driven. It is mechanically coupled to the drive head. Although the spin down motor is not configured to generate the very high torques that the hydraulic cylinder is designed to create, it is capable of rotating the drive head much faster than the hydraulic cylinder. In the preferred embodiment, the hydraulic spin down motor will typically generate about 500 ft lbs. of torque and rotate the drive head at about 585 rotations per minute (rpm""s). Torque from spin down motor may be improved, at the price of speed, by adding pulleys or gears as disclosed in U.S. application Ser. No. 09/302,836. The spin down motor is used to either spin the threaded member into a snug position during make up or to spin the threaded member until it is nearly or fully disengaged during break out. Examples of torque wrench assemblies incorporating hydraulic spin down motors may be found in U.S. patent application Ser. No. 09/302,836 and in PCT/US94/14715.
The valve of the present invention is configured to operate both the hydraulic torque wrench and the hydraulic spin down motor. It operates on a hydraulic system having pressurized line and a tank line. The pressurized line carries hydraulic fluid coming from the pump while the tank line returns the hydraulic fluid to the system reservoir. These lines enter the distribution block that houses the valve mechanism. They pass through a three position operator valve which controls how hydraulic fluid is directed through the combined wrench assembly.
The operator valve has three positions. In its center position, position A, the hydraulic fluid flow to the rundown motor is cut off as is the flow to the extension side of the hydraulic cylinder, while the retraction side is pressurized. In the left position, position B, the rundown motor is pressurized as is the retraction side of the hydraulic cylinder, while the extension side remains cut off from pressure. In the right position, position C, the retraction side is cut off from hydraulic pressure as is the rundown motor, while the extension side of the of the hydraulic cylinder is pressurized. The operator valve is preferably biased with a spring or other means to return to center position A when released by the operator. The preferred mechanisms for routing the hydraulic fluid through the distribution block to achieve the results described above is set forth in the detailed description of the preferred embodiment below.